Heat exchange system for patient temperature control with multiple coolant chambers for multiple heat exchange modalities

ABSTRACT

Cold plates through which refrigerant flows define a slot between them that can receive a cassette through which sterile working fluid with a relatively low flow rate flows from an intravascular heat exchange catheter. The working fluid from the catheter is heated or cooled by heat exchange with the cold plates through the walls of the cassette to maintain the sterility of the working fluid. On the other hand, high flow rate working fluid chambers surround the cold plates and non-sterile working fluid from an external heat exchange pad flows through the high flow rate working fluid chambers to exchange heat through direct contact with the cold plates.

FIELD OF THE INVENTION

The present application relates generally to heat exchange systems for patient temperature control with multiple coolant chambers for multiple heat exchange modalities.

BACKGROUND OF THE INVENTION

Patient temperature control systems have been introduced to prevent fever in patients in the neuro ICU due to suffering from sub-arachnoid hemorrhage or other neurologic malady such as stroke. Also, such systems have been used to induce mild or moderate hypothermia to improve the outcomes of patients suffering from such maladies as stroke, cardiac arrest, myocardial infarction, traumatic brain injury, and high intracranial pressure. Examples of intravascular heat exchange catheters are disclosed in U.S. Pat. Nos. 6,419,643, 6,416,533, 6,409,747, 6,405,080, 6,393,320, 6,368,304, 6,338,727, 6,299,599, 6,290,717, 6,287,326, 6,165,207, 6,149,670, 6,146,411, 6,126,684, 6,306,161, 6,264,679, 6,231,594, 6,149,676, 6,149,673, 6,110,168, 5,989,238, 5,879,329, 5,837,003, 6,383,210, 6,379,378, 6,364,899, 6,325,818, 6,312,452, 6,261,312, 6,254,626, 6,251,130, 6,251,129, 6,245,095, 6,238,428, 6,235,048, 6,231,595, 6,224,624, 6,149,677, 6,096,068, 6,042,559, all of which are incorporated herein by reference.

External patient temperature control systems may be used. Such systems are disclosed in U.S. Pat. Nos. 6,827,728, 6,818,012, 6,802,855, 6,799,063, 6,764,391, 6,692,518, 6,669,715, 6,660,027, 6,648,905, 6,645,232, 6,620,187, 6,461,379, 6,375,674, 6,197,045, and 6,188,930 (collectively, “the external pad patents”), all of which are incorporated herein by reference.

In the present assignee's U.S. Pat. No. 7,070,612, also incorporated herein by reference, a heat exchange console that could receive the coils of working fluid loops of both an intravascular heat exchange catheter and an external heat exchange pad was described and patented. In general, in all of the intravascular and external patient temperature control solutions, the temperature of the working fluid flowing through the catheter or pad is regulated by a heat exchange console based on feedback provided by the patient's actual body temperature, typically core body temperature as may be variously measured rectally, esophageally, tympanic ear temperature, blood temperature in, e.g., the vena cava, etc. The working fluid temperature is regulated by thermally coupling the working fluid to heating and/or cooling elements in the console.

SUMMARY OF THE INVENTION

As understood herein, the working fluid of external pads, unlike that of intravascular catheters, may not be required to be sterile. Furthermore, as understood herein, the working fluid flow rate of external pads may be significantly greater than the flow rates of sterile working fluid through intravascular catheters. With these recognitions in mind, in some applications it may be desirable to use the same heat exchanger with both a catheter and a pad but two different working fluid pathways within the heat exchanger with respective different characteristics tailored to their respective heat exchange modalities (internal intravascular heat exchange with the blood using a catheter and external heat exchange through the skin using a pad).

As used herein, unless otherwise specifically delimited by claim language, “pad” means any device configured for placement against a patient's skin through which a working fluid, also referred to herein as a “coolant” regardless of whether removing or adding heat to the patient, can flow to exchange heat with a human patient.

A heat exchanger includes at least first and second heat exchange plate assemblies defining a first modality working fluid chamber between them. The first modality working fluid chamber is configured for receiving a holder through which sterile working fluid can flow to and from a first modality patient heat exchange member such that the sterile working fluid can exchange heat with the plate assemblies through the holder without the sterile working fluid touching the plate assemblies. At least a second modality working fluid chamber is defined in the heat exchanger through which second working fluid can flow to and from a second modality patient heat exchange member such that the second working fluid from the second modality patient heat exchange member can exchange heat with at least one of the plate assemblies by directly contacting the at least one the plate assemblies.

The first modality patient heat exchange member can be established by an intravascular heat exchange catheter, and the heat exchanger may include the first modality patient heat exchange member. On the other hand, the second modality patient heat exchange member can be established by an externally-applied exchange pad, and the system can include the pad. The second working fluid from the second modality patient heat exchange member need not be sterile.

In some examples, the second modality working fluid chamber includes a first sub-chamber in the first plate assembly and a second sub-chamber in the second plate assembly. Each plate assembly can include at least one respective refrigerant passageway through which refrigerant can flow to heat or cool the respective plate assembly. In example embodiments, refrigerant must flow in series through the refrigerant passageways such that all refrigerant must flow first through the refrigerant passageway of the first plate assembly before flowing through the refrigerant passageway of the second plate assembly. In other examples, refrigerant flows in parallel through the refrigerant chambers. In contrast, in example embodiments the second working fluid must flow in parallel through the first and second subchambers. Or, the second working fluid may flow in series through the first and second subchambers.

In another aspect, a system has at least first and second plate assemblies through which refrigerant can flow through respective first and second refrigerant chambers. The plate assemblies define a slot between them that can receive first working fluid from an intravascular heat exchange catheter, so that the first working fluid from the catheter can be heated or cooled by the refrigerant flowing through the refrigerant chambers. The plate assemblies further include respective first and second working fluid chambers laterally outboard the respective first and second refrigerant chambers and configured for receiving second working fluid from an external heat exchange pad to facilitate heat exchange between the second working fluid and the refrigerant.

In another aspect, a system includes a first plate and a first working fluid chamber on a first side of the first plate. A first refrigerant chamber is on a second side of the first plate opposite the first side, such that heat exchange is facilitated through the first plate between the first refrigerant chamber and the first working fluid chamber. A second working fluid chamber is separated from the first refrigerant chamber by a wall through which heat exchange may be effected between the second working fluid chamber and the first refrigerant chamber.

The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a non-limiting system in accordance with the present invention;

FIG. 2 is a perspective view of an example working fluid cassette holder portion of a heat exchange system;

FIG. 3 is a perspective view of one half of the cassette holder shown in FIG. 2, with the opaque metal inner surface shown in transparency to reveal the serpentine refrigerant passageway;

FIG. 4 is a perspective view of an example working fluid cassette configured to engage the cassette holder shown in FIGS. 2 and 3;

FIG. 5 is a cross-sectional view as seen along the line 5-5 in FIG. 2; and

FIG. 6 is a cross-sectional view of an alternate embodiment as would be seen along the line 5-5 in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, in accordance with present principles, a system 10 may include an intravascular heat exchange catheter 12 controlled by a control system 14 to control patient temperature, e.g., to prevent the patient 16 from becoming febrile or to induce therapeutic hypothermia in the patient 16. In the catheter, working fluid (also referred to as “coolant”) such as but not limited to saline circulates (typically under the influence of a pump “P” in the control system) in a closed loop from the control system 14, through a fluid supply line L1, through the catheter 12, and back to the system 14 through a fluid return line L2, such that no coolant enters the body. While certain preferred catheters are disclosed below, it is to be understood that other catheters can be used in accordance with present principles, including, without limitation, any of the catheters disclosed above or in the following U.S. patents, all incorporated herein by reference: U.S. Pat. Nos. 5,486,208, 5,837,003, 6,110,168, 6,149,673, 6,149,676, 6,231,594, 6,264,679, 6,306,161, 6,235,048, 6,238,428, 6,245,095, 6,251,129, 6,251,130, 6,254,626, 6,261,312, 6,312,452, 6,325,818, 6,409,747, 6,368,304, 6,338,727, 6,299,599, 6,287,326, 6,126,684. The catheter 12 may be placed in the venous system, e.g., in the superior or inferior vena cava.

Instead of or in addition to the catheter 12, the system 10 may include one or more pads 18 that are positioned against the external skin of the patient 16 (only one pad 18 shown for clarity). The pad 18 may be, without limitation, any one of the pads disclosed in the external pad patents. The temperature of the pad 18 can be controlled by the control system 14 to exchange heat with the patient 16, including to induce therapeutic mild or moderate hypothermia in the patient in response to the patient presenting with, e.g., cardiac arrest, myocardial infarction, stroke, high intracranial pressure, traumatic brain injury, or other malady the effects of which can be ameliorated by hypothermia. The pad 18 may receive working fluid from the system 14 through a fluid supply line L3, and return working fluid to the system 14 through a fluid return line L4.

The control system 14 may include one or more microprocessors 20 receiving target and patient temperatures as input and controlling, among other things, the pump “P” and a refrigerant compressor 22 with a bypass valve 24 that can be opened to permit refrigerant to bypass the compressor. The refrigerant circulates through a heat exchanger within the control system 14 and described further below.

Indeed and now referring to FIG. 2, a portion of an example heat exchanger in the control system 14 is shown which includes at least two cold plates 30, 32 defining a cassette slot 34 between them. In one embodiment, the width “W” of the slot 34 is less than forty mils (0.040″), and may be between twenty nine mils and thirty one mils (0.029″-0.031″). In a specific example the width “W” may be thirty mils. As further detailed below, the slot 34 may establish a coolant chamber to receive a heat exchange member such as but not limited to a cassette through which working fluid from an intravascular heat exchange catheter flows. Because heat exchange is effected through the walls of the heat exchange member, the working fluid from the catheter does not contact any surface or fluid in the heat exchanger of the control system 14 outside the walls of the heat exchange member. In this way, the working fluid, typically saline in non-limiting examples, circulating through the intravascular catheter can remain sterile. Accordingly, attention will first focus on the coolant chamber established by the slot 34.

The cold plates 30, 32 may be made of metal, and can be rectilinear as shown and indeed may be nearly square. The cold plates 30, 32 may abut each other along left and right side walls 36, with elongated vertical cassette frame receptacles R1 and R2 being located immediately inboard of the respective side walls 36 and with the slot 34 extending between the walls 36 and terminating at the receptacles R1, R2 as shown. The frame receptacles R1, R2 may be wider than the slot 36.

In the example shown, refrigerant inlet and outlet tubes 38, 40 extend through at least one of the cold plates 32 to communicate refrigerant from a compressor into a refrigerant passageway in the cold plate, which establishes a second coolant chamber in addition to (and in thermal contact with) the first coolant chamber established by the slot 34. Each cold plate may have its own refrigerant inlet and outlet tubes, or, in the embodiment shown, only one cold plate may be formed with refrigerant inlet and outlet tubes and the other cold plate either thermally coupled to the cold plate in which the refrigerant flows and/or receiving refrigerant from the other cold plate through passageways formed through one or both of the side walls 36.

In one example, pad working fluid inlet and outlets P_(in) and P_(out) may also be formed in at least one of the cold plates as shown. As discussed in greater detail below, working fluid from the pad 18 via lines L3 and L4 may be ported into the pad working fluid inlet and outlets P_(in) and P_(out) to exchange heat with the refrigerant flowing through the cold plates. Also, to provide for warming working fluid, one or more electric heaters 41 may be mounted on one or both of the cold plates to heat the cold plates. Alternatively to warm the cold plates, the bypass valve 24 (FIG. 1) may be opened to allow hot gaseous refrigerant from the compressor to bypass the condenser as the gaseous refrigerant circulates through the system.

FIG. 3 shows details of an example cold plate 32 looking at the inner surface in transparency, it being understood that the inner surface typically is metal and that the serpentine refrigerant passageway 42 shown in FIG. 3 typically would not be visible to the human eye. In any case, the example refrigerant passageway that fluidly connects the refrigerant inlet 38 to the refrigerant outlet 40 may be serpentine-shaped as shown, or may be some other shape or pattern such as a herringbone pattern a wave pattern, etc.

FIG. 4 shows an example working fluid cassette 50 according to present principles. The cassette 50 is configured to fit snugly into the slot 34 and cassette frame receptacles R1, R2 defined between the cold plates 30, 32. Working fluid such as saline from a patient-engageable heat exchange member such as the catheter 12 flows through the cassette 50 in operation, with the working fluid exchanging heat with the refrigerant in the cold plates. In example embodiments, the cassette 50 is a low cost single-use disposable item that can contain, e.g., sterile saline which circulates through the catheter 12. The cassette may be placed by a medical caregiver in the slot 34 between the cold plates 30, 32 and the membrane portion which defines a space or working fluid chamber through which the example saline flows inflates when the working fluid flows through it, achieving thermal contact with the cold plates 30, 32.

In the example shown, the cassette 50 includes a frame 52 defining a periphery and a preferably rectilinear opening bounded as shown on at least three sides by the periphery of the frame. In the non-limiting example shown, the frame includes an elongated parallelepiped-shaped top rail 53 and elongated parallelepiped-shaped left and right side rails 54 parallel to each other and perpendicular to the top rail 32. The example frame 52 may have a metal strip or bottom rail 51 opposite the top rail and connected to the left and right side rails to support the membrane and facilitate placing the membrane in biaxial tension. In any case, the example frame 52 is rectilinear and is configured for being closely received between the two cold plates 30, 32, with the side rails 54 slidably engageable with the frame receptacles R1, R2 between the cold plates 30, 32 and with the below-described membrane assembly passed through the slot 36 to be in close juxtaposition with the refrigerant channels in the cold plates.

In FIG. 4, the frame, in the example shown, the top rail 53 thereof, is formed with a fluid inlet 56 in which an inlet tube 58 has been disposed and a fluid outlet 60 in which an outlet tube 62 has been disposed. Both the inlet and outlet establish respective fluid passageways through the frame into the opening. The inlet and outlet tubes 58, 62 may be engaged with the fluid return and supply lines L1, L2 that are associated with the catheter 12. The tubes 58, 62 may terminate at just below the top rail 53 (FIG. 4), or they may extend any desired length down to the bottom of the assembly, i.e., the tubes 58, 62 may extend almost the entire length of the left and right side rails 54, ending just above the below-described bottom seam of the membrane assembly.

Indeed, a polymeric membrane assembly 64 is connected to the frame 52, blocking the opening that is bounded on four sides by the frame as shown. The membrane assembly includes a first membrane 66 that is parallel to and closely spaced from a second membrane 68, leaving a space therebetween which establishes a working fluid chamber. The fluid inlet 56 and fluid outlet 60 communicate with the space between the membranes 66, 68. At least one and preferably both of the membranes 66, 68 are disposed in tension in the opening. The space between the membranes is expandable when filled with working fluid.

In one example, each membrane is no more than two mils (0.002″) thick and more preferably is between one mil and two mils in thickness (0.001″-0.002″), inclusive. The example preferred membranes 66, 68 are co-extensive with the opening and like the opening are more or less square, with the length of top and bottom edges of the example membranes being approximately equal (within ±10% and more preferably within ±5%) of the lengths of the left and right edges of the membranes. In other embodiments instead of a square (1:1) aspect ratio, an aspect ratio of up to 1:1.5 may be used. The working fluid chamber between the membranes is also rectilinear and in the preferred embodiment no obstructions exist between the membranes, meaning the working fluid chamber is a complete rectilinear, more or less square chamber.

Owing to the thinness of the membranes 66, 68 and the closeness of the cold plates 30, 32 to each other and to the membrane assembly between them when the cassette is engaged with the cold plates, the system shown in the figures affords low impedance of heat transfer between the refrigerant circulating in the cold plates and the working fluid circulating between the membranes 66, 68. The working fluid chamber between the membranes inflates due to backpressure generated by working fluid flow, eliminating or reducing the need for a moving mechanism in the cold plates. Moreover, the narrow slot 34 between the two cold plates provides better heat transfer by reducing the conductive path length between the cold plates and the working fluid. The frame allows for ease of handling, such as insertion and removal of the cassette with/from the cold plates.

With respect to the example working fluid chamber between the membranes 66, 68 having a width-to-length aspect ratio near 1:1 (i.e., square or nearly so), the amount of backpressure required to induce working fluid flow through heat exchanger is reduced compared to a less square configuration. This reduces the amount of work that a working fluid pump must perform, which is desirable for two reasons. One, since the pump may be disposable, lower performance requirements translate into a lower cost disposable and quieter system. For instance, peristaltic roller pumps offer quiet operation and a low-cost disposable element, but operate most efficiently when only modest pressures are required. Two, lowering the working fluid pump work reduces the amount of heat transferred into the working fluid by the pump itself. Also, a low width/length aspect ratio results in slower working fluid velocity which reduces amount of mixing, but this otherwise desirable (from a heat exchange standpoint) effect is negligible in the present example system since the Reynolds numbers are typically <1000, suggesting a laminar flow regime. Furthermore, a low width/length aspect ratio significantly reduces the number of bends (or “corners”) in the fluid flow path. These bends are areas of mixing for the fluid which promotes heat transfer. Without them, a fluid boundary layer builds up. However, this effect is offset herein by maintaining a narrow slot between the cold plates. This way the primary heat transfer mechanism is by conduction, but the conduction path length (and therefore boundary layer) is small, resulting in a relatively high rate of heat transfer.

In preferred examples, the membranes 66, 68 are stretched under tension during assembly to the frame, preferably biaxially (i.e., in tension between the top and bottom rails 53, 51 and also in tension between the left and right side rails 54). This tension can be maintained over the shelf life of the product. Pretensioning minimizes wrinkles in material, which is beneficial because wrinkles can impede working fluid flow and create air gaps which reduce heat transfer between the working fluid and cold plates. Wrinkles can also complicate insertion of the membrane assembly into the narrow slot 34.

To establish pre-tensioning of the membranes, the frame may be made in halves and posts such as threaded fasteners can extend transversely to one half of the frame, with the membranes 66, 68 being stretched over the posts and holes made in the membranes to receive the posts. The other half of the frame is then positioned to sandwich a rectilinear border portion of the membrane assembly between the frame halves, and a closure such as respective nuts engaged with the posts to hold the frame halves together with the membrane assembly held in tension between the frame halves. FIG. 4 shows that the working fluid chamber is closed off at the bottom by a bottom seam 74A of the membrane assembly, which is part of the border portion 74. In addition to applying tension to avoid wrinkling during use, additional posts may be used to avoid wrinkling during the welding process, improving the quality of the weld joints.

In the border portion 74, at least one and preferably more layers of polymer film may be used to reinforce the membranes 66, 68 to establish welded seams through which (at the sides of the membrane assembly) the post holes are formed, allowing for easier fabrication. By placing reinforcing layers on the border portion 74 only, the central “window” of the membrane assembly consists only of a single thin layer membrane ‘between the working fluid and one of the cold plates 30, 32 to minimize impeding heat transfer. A die-cut reinforcement layer may be used which reinforces the entire perimeter with one piece of material.

In some examples, the polymer membranes 66, 68 are highly stretchable, at least greater than 25% elongation. This allows the membranes to change from the empty flat state shown in FIG. 4 to an inflated shape (within the slot 34 between the cold plates) without wrinkling. It also allows the membranes to easily conform to features on the faces of the cold plates.

Additionally, the membranes may be made of a material which can also be made into tubing. Tubes such as the inlet and outlet tubes 58, 62 shown in FIG. 4 can then be thermally welded (e.g., using RF sealing) to the membranes, which is more reliable and quicker than adhesive bonding. The membranes 66, 68 need not provide their own lateral support because the cold plates 32, 34 and frame provide the support for the inflated membrane assembly, allowing it to withstand the pressure generated as a result of working fluid flowing through between the membranes. Structural features such as raised bumps, concavities, raised ribs, and so on may be located on the cold plates to optimize heat transfer. This can be economically advantageous because the cold plates are reusable components. Manifolds can be cut into the cold plates to even out the distribution of saline flow.

Having described an example non-limiting thermal exchange combination of structure between the heat exchanger in the control system 14 and the sterile working fluid in the intravascular temperature control catheter 12, attention is now directed to FIG. 5, which shows an example embodiment of additional coolant chambers in the cold plates by which to effect heat exchange with working fluid, including non-sterile working fluid, from the external heat exchange pad 18. Note that the plate structures shown in FIG. 5 preferably are metal or other material with high heat conductivity.

As shown, the cold plates 30, 32 may be multi-plate assemblies defining multiple fluid chambers, although in the discussion below they are referred to generally as “plates” 30 and 32. In the non-limiting example shown, the refrigerant inlet and outlet tubes 38, 40 extend through an outer wall 80 and a separator wall 82 of the cold plate 32 to communicate refrigerant from the compressor 22 into the refrigerant passageway 42 in the cold plate, which establishes a refrigerant chamber that is bounded by the separator wall 82 and an inner wall 84. On the other side of the inner wall 84 is the catheter working fluid cassette slot 34. As stated earlier, each cold plate may have its own refrigerant inlet and outlet tubes, or only one cold plate may be formed with refrigerant inlet and outlet tubes and the other cold plate either thermally coupled to the cold plate in which the refrigerant flows and/or receiving refrigerant from the other cold plate through passageways formed between the cold plates. In the example shown, the cold plates 30, 32 are thermally coupled through the side walls 36 (FIG. 2), a common bottom wall 86 (FIG. 5), and through the uninterrupted portions of a top wall 88 in which the slot 34 is formed.

In some examples, the cold plates 30, 32 are mirror image structures of each other. In the example of FIG. 5, the refrigerant chamber in the left-hand cold plate (32) is in fluid communication through refrigerant supply and return passageways 90, 92 with a refrigerant chamber 94 in the right-hand cold plate 30. Thus, the refrigerant chambers of the cold plates straddle the cassette slot 34 and are separated therefrom by respective inner walls 84, with refrigerant flowing serially through the left and right refrigerant chambers, first from the refrigerant inlet tube 38 into the left refrigerant chamber, then through the refrigerant supply passageway 90, the left hand refrigerant chamber 94, back through the refrigerant return passageway 92, and out the refrigerant outlet tube 40. This increases the refrigerant fluid flow rate through the refrigerant chambers, when two refrigerant chambers are provided as in the example shown.

In contrast, pad working fluid channel fluid flow may be plumbed in parallel to left and right pad fluid chambers which straddle the refrigerant chambers as shown and are separated therefrom by respective separator walls 82. In the non-limiting example shown, fluid from the external pad flows through the pad working fluid inlet Pin into an inlet plenum 100 formed in the bottom wall 86. The fluid flows in parallel through inlet ports 102, 104 into left and right pad working fluid chambers 106, 108. The fluid exits the pad working fluid chambers through an upper plenum 110 formed in the top plate 88 and out of the working fluid outlet Pout back to the external pad. This example parallel fluid flow reduces backpressure in the pad working fluid system.

Note that the above-described series fluid flow through the refrigerant chambers and parallel flow through the pad working fluid chambers is exemplary only, and is not limiting. Thus, fluid flow through the pad working fluid chambers may be in series and/or fluid flow through the refrigerant chambers may be parallel. Note further that the particular example plumbing arrangements illustrated and described are but one example of plumbing fluid through the multi-chamber cold plates 30, 32.

Indeed, FIG. 6 shows a system similar to the one shown in FIG. 5, except that fluid flow through the refrigerant chambers is in parallel. Both refrigerant chambers may communicate with a refrigerant inlet plenum 200 through which refrigerant flows into each refrigerant chamber 94 in parallel. Also, both refrigerant chambers may communicate with a refrigerant outlet plenum 202 through which refrigerant flows out of each refrigerant chamber 94 in parallel back to the compressor.

It may now be appreciated that in the intravascular heat exchange mode, working fluid from the catheter 12 flowing through the cassette 50 which is disposed in the slot 34 exchanges heat with the refrigerant in the refrigerant chambers 42, 94 through the respective inner walls 84. The catheter working fluid comes into contact with no portion of the cold plate heat exchanger, owing to it flowing through the cassette 50. In this way, the catheter working fluid retains its sterility and is enclosed in a closed fluid circuit for withstanding circulation fluid pressures of, e.g., seventy pounds per square inch (70 psi).

On the other hand, since pad working fluid is separated from the patient by an external pad, it may not require sterility, in which case the pad working fluid contacts the separator plates 82 directly in the cold plates 30, 32 to exchange heat with the refrigerant in the refrigerant chambers 42, 94.

While the particular HEAT EXCHANGE SYSTEM FOR PATIENT TEMPERATURE CONTROL WITH MULTIPLE COOLANT CHAMBERS FOR MULTIPLE HEAT EXCHANGE MODALITIES is herein shown and described in detail, the scope of the present invention is to be limited by nothing other than the appended claims. 

What is claimed is:
 1. Heat exchanger, comprising: at least first and second plate assemblies defining a first modality working fluid chamber between them, the first modality working fluid chamber being configured for receiving a holder through which sterile working fluid can flow to and from a first modality patient heat exchange member such that the sterile working fluid can exchange heat with the plate assemblies through the holder without the sterile working fluid touching the plate assemblies; and at least a second modality working fluid chamber through which second working fluid can flow to and from a second modality patient heat exchange member such that the second working fluid from the second modality patient heat exchange member can exchange heat with at least one of the plate assemblies by directly contacting at least one of the plate assemblies, wherein at least the first plate assembly includes at least one refrigerant passageway through which refrigerant can flow to heat or cool the first plate assembly, the refrigerant not being the sterile working fluid or the second working fluid.
 2. The heat exchanger of claim 1, wherein the first modality patient heat exchange member is established by an intravascular heat exchange catheter.
 3. The heat exchanger of claim 1, comprising the first modality patient heat exchange member.
 4. The heat exchanger of claim 1, wherein the second modality patient heat exchange member is established by an externally-applied exchange pad.
 5. The heat exchanger of claim 1, comprising the second modality patient heat exchange member.
 6. The heat exchanger of claim 5, wherein the second working fluid from the second modality patient heat exchange member is not sterile.
 7. The heat exchanger of claim 1, wherein the second modality working fluid chamber includes a first sub-chamber in the first plate assembly and a second sub-chamber in the second plate assembly.
 8. The heat exchanger of claim 1, wherein refrigerant must flow in series through the refrigerant passageways such that all refrigerant must flow first through the refrigerant passageway of the first plate assembly before flowing through the refrigerant passageway of the second plate assembly.
 9. The heat exchanger of claim 1, wherein refrigerant can flow in parallel through the refrigerant passageways.
 10. The heat exchanger of claim 7, wherein the second working fluid must flow in parallel through the first and second subchambers.
 11. System comprising: at least first and second plate assemblies through which refrigerant can flow through respective first and second refrigerant chambers, the plate assemblies defining a slot between them that can receive first working fluid from a catheter, so that the first working fluid from the catheter can be heated or cooled by the refrigerant flowing through the refrigerant chambers; and the plate assemblies further including respective first and second working fluid chambers laterally outboard the respective first and second refrigerant chambers and configured for receiving second working fluid from a heat exchanger configured for exchanging heat with an external surface of a patient to facilitate heat exchange between the second working fluid and the refrigerant.
 12. The system of claim 11, wherein the slot is configured for receiving a cassette through which the first working fluid can flow so that heat can be exchanged between the plate assemblies and the first working fluid without the first working fluid contacting the plate assemblies.
 13. The system of claim 11, comprising the catheter.
 14. The system of claim 11, comprising the heat exchanger configured for exchanging heat with an external surface of a patient.
 15. The system of claim 11, wherein refrigerant can flow in series through the refrigerant chambers such that all refrigerant can flow first through the refrigerant chamber of the first plate assembly before flowing through the refrigerant chamber of the second plate assembly.
 16. The system of claim 11, wherein refrigerant can flow in parallel through the refrigerant chambers.
 17. The system of claim 11, wherein the second working fluid can flow in parallel through the first and second working fluid chambers.
 18. System comprising: first plate; first working fluid chamber on a first side of the first plate; first refrigerant chamber on a second side of the first plate opposite the first side, such that heat exchange is facilitated through the first plate between the first refrigerant chamber and the first working fluid chamber; and second working fluid chamber separated from the first refrigerant chamber by a wall through which heat exchange may be effected between the second working fluid chamber and the first refrigerant chamber.
 19. The system of claim 18, comprising: second plate, the first working fluid chamber being between the first and second plates; second refrigerant chamber on a side of the second plate opposite the first working fluid chamber, such that heat exchange is facilitated through the second plate between the second refrigerant chamber and the first working fluid chamber; and third working fluid chamber separated from the second refrigerant chamber by a barrier through which heat exchange may be effected between the third working fluid chamber and the second refrigerant chamber. 